1. Field of the Invention
The present invention relates to a chopper assembly for cutting fibers into short lengths and is particularly applicable to the severing of glass fiber strands. More particularly, the present invention relates to a blade roll for use with the chopper assembly.
2. Description of Prior Art
Heretofore it has been known to sever linear materials into regular lengths by passing the material between a backup roll and a blade roll with a series of blades mounted and spaced evenly about its periphery and projecting radially therefrom.
A typical prior art blade roll comprises a stainless steel cylindrical member which has been milled with a plurality of slots. Cutting blades are subsequently positioned within the milled slots. In the past, the slots have been milled to have a thickness larger than the section of the chopper blade to be mounted therein in order to avoid the excessive cost of milling each slot to the exact width of an individual chopper blade. By milling the slots to be somewhat larger than the chopper blades, (e.g 0.002-0.004 in. as taught in U.S. Pat. No. 3,869,268) the blades tend to vibrate within the slots during the operation of the blade roll. This vibration causes the chopper blades to wear more rapidly and thus shortens the effective life of the chopper blade. The prior art as disclosed in U.S. Pat. No. 3,508,461 in order to more firmly hold the chopper blades in position in the blade roll, incorporated a resilient gasket which is mounted in contact with the end edges of the blades positioned in the blade roll and by an end cap which is fastened securely to the blade roll. It is necessary to tightly fasten the end caps against the gasket in order to rigidly fix the blades so as to prevent their outward movement from the blade roll member, but this often results in the blades cutting through the resilient gasket entirely. This cutting or tearing apart of the gasket not only destroys the ability of the gasket to retain the chopper blades in position, but also creates other hazards as well since fragments of the gasket may fly out and contaminate the material being chopped or may actually strike an operator of the chopper assembly.
U.S. Pat. No. 3,664,109 discloses protrusions 51 and 51A to restrain movement in a circumferential direction.
U.S. Pat. Nos. 3,130,619 and 3,118,336 disclose blade rolls which are comprised of plastic or rubber like materials, but neither reference suggests milling slots in the blade roll to support the blades. More particularly, U.S. Pat. No. 3,118,336 utilizes a complex system of wires to hold embedded blades in position. U.S. Pat. No. 3,130,619 also embeds a plurality of blades in its blade roll which is preferably comprised of Teflon (registered Tradmark of E. I. DuPont). Embedding the blades in the blade roll material has several disadvantages, including a more costly initial construction, and the inconvenience and difficulty of replacing worn out blades.
Accordingly, it is an object of the present invention to overcome the disadvantages of prior art blade rolls by providing a blade roll which increases the effective chopping life of the blades.
It is a further object of the present invention to provide a blade roll for use in a chopper assembly which substantially eliminates undesirable vibration of the chopper blades mounted within the blade roll member.
Accordingly, the present invention provides a cylindrical blade roll having an axis of rotation along its center line for use in a chopper assembly for cutting fibers into short lengths comprising a blade roll cylinder member; a plurality of chopper blades projecting generally radially therefrom, each of the blades having a cutting edge, a base portion, and two sides; and blade retaining means. In the preferred embodiment, the blade roll cylinder member comprises a rotatable core having a resilient, durable elastomer affixed about the outer circumferential surface of the core wherein the elastomer has a cylindrical outer surface configuration with a plurality of milled slots extending generally lengthwise of the blade roll cylinder member. These milled slots have a thickness slightly less than the greatest thickness of the portion of the chopper blades inserted into the slots so that the sides of the slots tend to grip the portion of the chopper blades.
The present invention further provides an improved blade retaining means comprising an annular blade retainer positioned at each end of the blade roll cylinder member wherein a side surface of each of the blade retainers has at least one annular groove therearound which in the preferred embodiment is situated radially inwardly of the outer diameter of the blade roll cylinder member when the center line of the blade retainer is in alignment with the center line of the blade roll cylinder member. A blade retaining ring is positioned partially within the at least one annular groove of each blade retainer so that the blade retaining rings engage the chopper blades at each end thereof to restrain the chopper blades against movement in a circumferential direction.